1. Field of the Invention
The present invention relates to a vehicle lighting apparatus and in particular to a vehicle lighting apparatus using a discharge bulb as a light source in which noise generated when the discharge bulb is turned on is effectively shielded.
2. Background Art
In recent years, a vehicle lighting apparatus including a discharge bulb as a light source has been used. By using the discharge bulb, high luminous intensity can be obtained with smaller power consumption than a related art bulb. Such a vehicle lighting apparatus with the discharge bulb has a problem that electromagnetic noise generated by the discharge bulb has an influence on operations of various electronic circuits in a vehicle.
Thus, it has been proposed to provide electromagnetic noise shielding means on the vehicle lighting apparatus in order to protect the electronic circuits from the electromagnetic noise generated by the discharge bulb (for example, refer to Patent Reference 1).    [Patent Reference 1] JP-A-2000-243105
Patent Document 1 discloses a vehicle lighting apparatus in which a shielding effect of the electromagnetic waves is enhanced, the number of parts is reduced, and a corresponding assembly work is simplified.
The vehicle lighting apparatus includes a connector to be attached to and detached from the plug of the discharge bulb supported by a reflector. In part of the periphery of the reflector where the connector is fitted, a contact terminal part electrically connected to a conductive film (shield part) covering the reflector is provided. To the connector, a conductive cover (shield part) covering the connector is integrated. The conductive cover comes into contact with the contact terminal part with the connector fitted to the plug.
When the connector is fitted to the plug, the conductive cover is automatically brought into electric connection to a contact terminal electrically connected to the conductive film of the reflector to deliver shielding effect. This eliminates the need for independent shield parts and corresponding assembly work.
Further, when the connector is fittingly attached to the plug of the discharge bulb, the connector is fitted to the rear of the plug and rotated in a circumferential direction of the plug to integrate the plug and the connector. That is, the connector is rotated in circumferential direction to cause a contact part arranged on a peripheral surface of the conductive cover designed to cover the connector to come into contact with a contact terminal part to establish electric connection between the contact part and the contact terminal part.
However, when the connector is fitted to the plug of the discharge bulb and rotated in a locking direction, the discharge bulb is also rotated together and may be displaced from a predetermined position thus failing to obtain predetermined light distribution.
Further, a flange of the plug of a discharge bulb has a positioning notch formed thereon to fit to a positioning rib arranged in a bulb fitting opening of the reflector for positioning of the discharge bulb in the circumferential direction. A clearance is necessary between the positioning rib and the positioning notch in consideration of easy assembly.
As a result, when the connector is fitted to the plug of the discharge bulb and rotated in the locking direction, the discharge bulb is also rotated together in the circumferential direction within a range of the clearance. This causes variations in the fitting position of the discharge bulb in the circumferential direction. This could result in variations in the light distribution of the vehicle lighting apparatus despite the presence of the positioning rib.